The present invention generally relates to a switching device for electronic circuits and, more particularly, is concerned with a small, low cost and highly reliable switch which utilizes elastomer elements to connect, disconnect or transfer the current between one or more circuits within an electronic device.
Because of the importance of switches to the operation of many electronic circuits and electronic devices, there have been a large number of technological approaches taken to the design of switches. These technological approaches range from simple rotary switches and other electro-mechanical switching devices to the more complex optical switching and plasma switching devices. The traditional, and more common, approaches involved the use of mechanical devices or solid state electrical components to connect, disconnect or transfer the current between one or more circuits within an electronic device.
A related and somewhat modern approach to the design of switching devices involves the use of conductive rubber or elastomers as part of an electro-mechanical switching mechanism. The conductive rubber switching mechanisms use generally non-conductive rubber material which becomes electrically conductive when subjected to mechanical forces such as compression or tension.
There also exist many varieties of elastomer membrane switches and other pushbutton switches or keyboard switches which utilize conductive elastomers. One such example is an elastomer dome keypad switch which includes a layer of elastomeric material having domes located at predetermined positions. Located in the center of the domes is a piece of conducting elastomer. Collapsing a dome causes the conducting elastomer to contact switch elements formed on the surface of an underlying printed wire board.
As the size of many electronic devices and circuitry diminishes, the design considerations of a switching device for use with the smaller electronic components becomes more of a challenge. The switching devices used in small electronic devices such as telephones, receivers, transmitters, detectors, and controllers, should preferably demonstrate a high reliability, a relatively low cost, improved maintainability characteristics, and efficient use of space both for the switching device and the associated connections. A preferable switch would also be simple in design which can be easily incorporated into the assembly process of the host electronic device.